In the most varied areas of applications such as fabrication, maintenance, analysis, stock keeping etc. it is desired more and more to equip movable objects with automatically readable identification means. Such identification means is e.g. used for automatic identification of the objects. Automatically readable identification means are e.g. markings readable with optical means or electronically stored data.
Optical markings are e.g. bar codes. Reading of such optical identification means is carried out without contact, whereby a reading distance and a reading angle must be maintained within a given range and whereby the marking must be visible, i.e. not separated from the reading equipment by a non-transparent medium.
Electronically stored data is e.g. stored in a corresponding integrated circuit which circuit is attached to the object to be identified. For reading the stored data, this kind of circuit is contacted by a reading device or by a probe of such a device or it comprises an antenna and the stored data are read without contact by a appropriately equipped reading device. Circuit, antenna and reading device can be designed such that the data which is stored in the circuit can not only be read by the device but can also be overwritten (reading/writing device) and also such that the energy required in the circuit for reading or overwriting is transmitted from the device to the circuit without contact such that no special source of energy (e.g. battery) is required for the circuit on the movable object.
In contrast to the optical markings, electronically stored data can take over a controlling function as well as an identifying function, i.e. with the help of such data suitably equipped devices can be triggered directly.
For data communication with contact, the reading/writing device and the object are to be brought into a precisely defined relative position. Data communication without contact is possible in more or less freely selectable relative positions of object and reading/writing device depending on the design of circuit, antenna and reading/writing device. However, in a system with a large freedom concerning the position of the reading/writing device it is more difficult or no longer possible without further means to restrict the data communication to one specific object or to functionally couple a locality with an object (for localizing objects and/or for control functions to be taken over by objects being present in one specific position).